ECN Forum Forums Code Related Discussion NEC & other Code issues Bonding of metal studs

Florida's code section seems pretty straightforward and clear to me. In the 'definitions' section of the code some language could be added to differentiate between structural steel (intended to be a load bearing component of the structure) and 'steel framing' (non-load bearing, structurally designed to support interior walls or partitions).

I am still not sure why this isn't a 250.104(C) situation.

I don't know... I kind of went round and round with that same thought before I originally posted, but the reason that I didn't feel that 250.104[C] applied here was because it mentions structural metal that forms a building frame and that this framing must be bonded at the service enclosure or the grounding electrode conductor at the service, etc... and that the points of attachment must be accessible, so it doesn't sound like it was intended here. It also refers back to 250.64, which doesn't really seem like it would relevant here either. I don't think that the reference to Table 250.66 would be correct here either even though it is about bonding conductors. If it were, we would have to pull a minimum #8 back to the service to bond metal stud walls, which I hope isn't true because that would be insane.
I would think 250.122 would be more inline instead, even though it is for EGC sizing, not bonding conductors.
Another thing that I'm not sure there would be any provision or exception to allow for the use of metal box as a means for bonding the stud walls.


At the moment, the articles I feel most closely apply, so far, are 250.4, 250.8 and 250.102, but of course, subject to change as things progress.
Who would of thought that something as simple as bonding interior metal stud walls could be such a terror to explain in NEC.

Metal studs may not normally be load bearing, but they're still structural and just as likely to become energized.

In many applications, they are load bearing. Why should we consider them differently from one application to another just because of vertical load? Loading of the members makes no difference to the electrons.

I think the real issue is "exposed"(per 250.104(C)) Electrically, as soon as you put a metal cabinet, door or window frame in there that is accessible to the user, the stud is exposed.
Florida is giving you a break by allowing 250.122 bonding based on the circuit likely to energize.

I truly hope that they are categorized differently because if not, they would be subject to 250.104[C] and 250.104[D],2 which would mean a bonding conductor brought back to the service entrance and could also allow metal stud walls to be used as a grounding electrode for a transformer, as Reno pointed out earlier, since there could be a separately derived system serving one area of a building.
The thin gauge stamped steel studs walls are held together with short self-tapping sheet metal screws and could be required to carry a tremendous amount of fault current under the wrong circumstances. This is not very safe or adequate IMO.

I am not sure 250.104(C) implies this is a 250.52(A)(2) ground electrode although it is bonded that way.
I assume they do that because they are not defining the circuit likely to energize. If you think the 60a to the heaters in the air handler or the range is a candidate, a #10 is not unreasonable. I still think if you just used a metal box for the dryer, the range and the couple required GFCI outlets you are covered. Those are generally where your hazards are. (bath, kitchen, laundry and garage/basement if there are steel studs.)
Then pick up any wall segments you haven't hit. This is the kind of thing a decent CAD program could highlight on the plan.

At the risk of being repetitive ... why not address the porblem at the source - and ban Romex from light steel construction? How many 'band-aids' will we ultimately need to compensate for an inadequate wiring method?

I doubt you will get much traction in banning RX in 1&2 family. The NFPA seems to be going the other way.

Metal studs are no different than screw-set couplings with respect to impedance and quality of bonding, yet the latter are considering adequate for grounding...

If I was writing the code book, I would require ground wires to be run with every circuit so that none of this other metal is primary fault grounding path... but I would still required it to be bonded to ground. I like the florida code, too, that allows them to be bonded to the largest circuit they're liable to be energized with. If only 20A runs are near that wall, #12 is fine for bonding, etc.

If properly run (with grommets or strain relief couplings, etc), steel studs are no more dangerous to romex that metal panel enclosures or handy boxes. Just because somebody "might" get lazy with it and ignore the rules is no reason to ban it.